An unmanned aerial vehicle makes a flight based on an automatic algorithm, and thus has to automatically take off and land to achieve a perfect automatic system. In case of mountainous areas, a distance required for landing is so short that methods usable for recovery are limited. However, there is no automatic recovery method of using a net to effectively recover the unmanned aerial vehicle within a short distance in the existing research.
The net recovery needs a higher degree of precision than other recovery methods because a recovery point and range are set to be about 2˜3 times larger than the size of a flight vehicle. If a differential global positioning system (DGPS), a laser and radar are used, it is possible to ensure high precision. However, topographical conditions of mountainous area are improper to use a signal of the DGPS, and a method of using the laser or radar is also disadvantageous since a construction cost is high and self technology development is difficult even though it has high precision.
Also, a method of using vision information has advantages that construction and development costs are low and precision within a short distance is high. However, in the case of using only the vision information, it is disadvantageously difficult to control an altitude because only a relative location and a distance are used.
Further, there is a method of employing a reference trajectory. In the case of using the reference trajectory, it is advantageously possible to maintain an altitude optimized for flying toward an aiming point because an optimum path of connecting given start and end points is generated and traced. However, it is disadvantageously difficult for the net recovery to provide such high precision since the recovery point and range are set to be about 2˜3 times larger than the size of a fight vehicle.